Copper oxide-alumina catalyst composition



United States Patent ()fiice 3,374,183 Patented Mar. 19, 1968 3,374,183COPPER OXIDE-ALUMINA CATALYST COME'OSITION Douglas E. Cooper,Birmingham, Mich, assignor to Ethyl Corporation, New York, N.Y., acorporation of Virginia No Drawing. Continuation-impart of applicationSer. No. 26,698, May 4, 1960. This application Mar. 30, 1961, Ser. No.99,340 i 15 Claims. (Cl. 252-463) This invention relates to a novelmethod of preparing supported catalysts and to novel catalysts preparedthereby. While many catalysts can be prepared by various well-knownmethods, a smaller number can be advantageously prepared by veryspecialized techniques. One usual manner of catalyst preparation is toimpregnate the carrier material with a solution of a salt of the metal,followed by appropriate treatment to convert the metal salt to thedesired active form. For example, if the active form is an oxide, thecarrier material is impregnated with a suitable metal salt and is thenroasted to yield a product bearing an oxide or oxides of the metal, Ifthe finished catalyst is to contain the active agent in a pure metallicstate, the oxide formed can be reduced in a hydrogen atmosphere to yielda catalyst composed of the carrier material impregnated with the metal.If a catalyst containing a plurality of metals or oxides is desired, thestarting material may be a common solution of the salts of both metals,or the carrier may be impregnated successlvely with separate solutionsof the metal salts. Also, a finished metal or metal oxide catalyst maybe impregnated with a solution of other metal salts and then againsubjected to a roasting step.

This application is a continuation-impart of my earlier filedapplication Ser. No. 26,698, filed May 4, 1960, now abandoned. I

While the method described above is satisfactory for the preparation ofmost catalysts, with some metals, complications become obvious. Theavailable metal. salts may be prohibitively expensive;'they may not besoluble to a degree to allow sufficient amounts of metal to be depositedon the carrier material, or the reaction products and gases evolvedduring the subsequent roasting period may be noxious, corrosive, orpoisonous. Moreover, diliiculties may be encountered in converting somemetal salts to the active oxide form. In such cases it becomes necessary to revert to specialized techniques of catalyst preparation.

, It is an, object of this invention to provide a novel method ofpreparing supported copper oxide catalysts. By

the use of my invention, novel and unexpectedly superior copper oxidecatalysts are prepared. Moreover, this technique provides a superiormethod of preparing such catalysts without encountering any of theproblems enumerated above. Among the advantages of using my techniqueare:

(1) Inexpensive and readily available starting materials. (2) Highconcentrations of the copper salt can be put in the solution.

I (3) Recycling some of the recoverable gases evolved dur- One of themost outstanding features of the novel catalysts of this invention istheir resistance to abrasion and attrition due to physical and thermalshock. I have b served that catalysts made by my method have a hardersurface than previous catalysts. In this respectcatalysts prepared bythe method of this invention are vastly superior to similar catalystsprepared by more conventional means. My new catalysts were tested inspecial mufilers attached to modern automobiles wherein they werecontinually subjected to the physical and thermal shocks inherent insuch an application. The results were excellent, the catalyst showingvery little tendency to chip, craze, or powder. However, with'asuperficially similar catalyst prepared by a more conventional methodnot of this invention, catalyst attrition in the form of chipping,crazing, and powdering was very evident after only a relatively shortperiod of operation. In fact, at this point the catalyst haddeteriorated to such an extent that much of the catalyst material, in apowdery form, had been carried along with the exhaust gas and dischargedto the atmosphere. I

According to the present invention, I provide a novel method ofpreparing copper oxide catalysts supported on certain transitionalalumina carriers, which are described in detail below. I also providenovel and impregnated catalysts which comprise copper oxide-transitionalalumina compositions prepared by my novel method. Optionally, one ormore additional metals may be incorporated in my new catalysts aspromoters. My new catalysts are especially suited for the exodation ofundesirable ingradients in the exhaust gas stream of internal combustionengines.

According to my method, I convert a starting copper material selectedfrom the class consisting of oxygencontaining salts of copper, includingbasic salts, oxides of copper, and copper hydroxide to deeply-colored,highly water-soluble, copper-ammonia complexes. I then impragnate atransitional alumina of the type described below with a solution of thecomplex salt. I thereby produce, after heating to decompose thecopper-ammonia complex and drive-01f volatile materials, a highlyunusual and unique catalyst One of the more important advantages of mymethod is that it permits use of insoluble starting copper compounds.Many of these are among the cheapest available copper compounds, butthey cannot be used to form catalysts by conventional methods.

Among the oxygen-containing salts of copper which I use as startingmaterials are acetate, benzoate, carbonate, chromate, nitrate, formate,lactate, oxalate, sulfate and the like. I can use some of these salts ineither the normal or basic forms. The basic carbonates are especiallydesirable materials. I can use cupric and cuprous oxides as well ascopper hydroxide.

The reagent with which I react my starting copper compound to form thecopper-ammonia complex is either ammonia or ammonium hydroxide. The mostdesirable form of copper-ammonia complex which I useis that in which theanions are entirely carbonate ions. For example, I may start with thewe1l-known CuCO Cu(OH) and add additional carbonate ions, possible using00,, or preferably in the form of ammonium carbonate so as to provideone carbonate ion for every cupric ion present in the complex. I thenusually prefer to treat the carbonate solution with enough of eitherammonia or ammonium hydroxide to complete the formation of the complexsalt.

There are two cupric amine complexes commonly recognized in the art.These are diarnmine copper II, Cu(NH and tetrammine copper II, Cu(NH Adiam'mine cuprous ion, [C11(NH3')2] is also recognized. All three ionsform highly water-soluble salts and are deep violet in water solution. Ican use either of them to form my new catalysts. Which of the coppercomplexes I usedepends upon the particular anion I employ. In thepreferred case of carbonates, the tet-rammine cupric salt is much moresoluble and thus, in most cases, more desirable. With copper acetate Ican obtain a highly soluble diammine cupric salt, Whereas starting withcupr-ous oxide,'the diammine cuprous salt is formed.

In any event'I must always use at least enough ammoniacal reagent tocompletely convert all the copper present to either the diammine ortetrammine form, as the case may be. This is equivalent to 2 moles ofammonia for every mole of copper converted to the diammine form and 4moles of ammonia for each mole of copper to be converted to thetetrammine form. Although it is not necessary, ordinarily I prefer touse a slight excess of ammonia to insure complete conversion of copperto the complex. As stated above, when the starting copper com pound is abasic copper carbonate, I use an additional source of carbonate ions,preferably ammonium carbonate or carbon dioxide. The amount of suchadditional agent must be at least enough to convert all copper presentto the carbonate form. I then use a slight excess to insure completeconversion to carbonate.

The a bove stoichiometric conclusions can be illustrated byconsideration of preparation of catalyst from one of my preferredstarting materials; namely, malachite, which is .a form of basic coppercarbonate. (Other inexpensive and commercially available basic coppercarbonates which I prefer to use are azurite, [2CuCO -Cu(OH) and amixture of malachite and azurite.) The equation for conversion ofmalachite to its tetrammine complex is:

CuCOzCMOH); (NHmCOa, GNHiOH (insoluble) 2Cu(NH3)4CO 81120 (soluble) Asdefined by the above reaction, in order to completely convert the basiccopper carbonate to the copper ammonia complex form, one mole ofammonium carbonate and 6 moles of ammonium hydroxide are required permole of basic copper carbonate. The complete conversion of the basiccopper carbonate to the copper complex form is indicated by a clear,deeply-colored violet solution, as contrasted with a cloudy somewhatpaler-colored solution if the conversion is incomplete. It is importantthat the basic copper carbonate be completely converted so as to avoidthe deposition of .a precipitate material on the catalyst carrier. Toassure a complete conversion to the complex form, I often use an excessof ammonium carbonate and ammonium hydroxide, either by having a largervolume, or a more concentrated solution than isstoichiomet-rically.required. The stoichioinetry involved in use ofother copper starting materials and other ammo niacal reagents will beapparent from the above to those skilled in the art.

The above reactions, exothermic in nature, are not critical with respectto temperature and pressure. They can be easily carried out over a widetemperature range and most conveniently the reactions can be carried outstarting at room temperature and at atmospheric pressure.

'The reagents that I use to convert the starting copper material to thehighly soluble, deeply-colored, copperamm-onia complex may be a gas(ammonia), a solid (ammonium carbonate), or a solution (ammoniumhydroxide). Ordinarily, it is most convenient to use a solutiondorrn ofmy reagent or reagents. When using a mixture of-reagents such as ammomum'hydroxlde and ammonium carbonate, I usually combine these two first andthen add the basic copper salt. In other cases I have mixed the powderedammonium carbonate with the copper carbonate and then added the aqueousammonium hydroxide. Another method is to pass the appropriate amounts ofcarbon dioxide and ammonia into a suspension of the copper salt inWater.

Having prepared the copper-ammonia complex, I next use it to prepare thecatalyst of my invention. One way of doing this is as follows:

The carrier material is immersed in or otherwise contacted with theclear, violet-colored solution of the copperammonia complex andallowedto become thoroughly impregnated. This step can be accomplishedin a minimum of time, usually less than one-half hour. The impregnatedcarrier material, either removed from or together with remaining coppercomplex solution, is subjected to gradual heating up to about 300 C.During this heating period, carbon dioxide, ammonia, and water areevolved. Roasting in the ordinary sense is not necessary. However, theheating can be conducted in the presence of oxygen if desired. Theammonia and carbon dioxide may either be recovered or they may berecycled if a continuous process is developed.

The carrier material used for my catalysts consists of an activatedtransitional alumina having a surface area of at least square meters pergram (m. g.) and containing from 0.01 to about 5 percent silica. Thisspecific type of alumina is critical to my invention. The aluminareferred to is activated alumina to be contrasted with ordinary aluminumoxides which cannot be used in the catalysts of this invention. Theactivated alumina is an active desiccant, has active adsorbingcharacteristics and has the ability to catalyze certain hydrogenationand dehydrogenation reactions; whereas, ordinary aluminum oxides such asthose prepared from aluminum hydroxide are essentially void of theseproperties. Likewise, the use of materials such as porcelain chips,silica gel, pumice, and quartz and the like result in vastly inferiorcatalysts and cannot be used as the carrier material for the catalystsof this invention. V

Generally, the carrier material serves as a support or a binder for theactive catalytic agent, but in itself has little, if any, catalyticactivity for the reaction in question. Other mechanical functions mightbe to impart physical strength and to serve as an aid in the dissipationof heat to prevent sintering. For such purposes, any one of thewell-known carrier materials may be equally effective. Aside from purelymechanical functions, a carrier material may serve to give a largerexposure of the catalytic agent, increase thermal stability, modifycatalytic selectivity and give increased resistance to poisoning of theactive agent. Also, a complex formation may take place between thecarrier and the active agent which results in an overall material thathas better catalytic properties per unit area than the active agentalone. It is because of these non-purely mechanical functions that acarrier material may be specific for a given catalytic agent withrespect to a particular reaction; that is, although a catalytic agent onone carrier material may be an excellent catalyst for a specificreaction, it may behave entirely diiferent and be a poor catalyst ifsupported by a different carrier material.

I have found that copper oxide-transitional alumina catalysts preparedby the method of this invention are excellent catalysts for theoxidation of unburned hydrocarbons and carbon monoxide found in theexhaust gas streams of internal combustion engines. However, catalystscomposed of copper oxide on other well-known catalyst carriers and,indeed, even on other grades of aluminas, result in inferior catalysts.In other words, a particular grade of activated alumina carrier isspecific for copper oxide for the oxidation of the hydrocarbons andcarbon monoxide found in the exhaust stream of internal combustionengines.

One of the most striking and unusual features of my catalysts is thecritical nature of the alumina which is employed as a carrier or base.The broad spectrum of aluminas, in general, cannot be usedindiscriminately; only certain highly select and specific types ofaluminaare useful. The aluminas which are used as carriers in myinvention can be described as transitional aluminas. They are metastableforms which, in general, are produced by heating of alpha or betaalumina trihydrates or of alpha alumina monohydrate. As each of thesestarting materials, or any mixture thereof, is heated, phase changestake place. A number of intermediate or transitional alumina phases areformed. These are characterized by being only partially or poorlycrystalline. They are partly amorphous and partly crystalline. Formationof these phases is reversible. On rehydration, they can be convertedback to the starting materials. On prolonged heating, particularly atvery high temperatures such as 1150 C., they are converted into theso-called alpha alumina which is a stable, refractory type of aluminanot applicable to this invention. Conversion of the transitional formsof alumina to the alpha form is irreversible and any substantialconversion to this form is to be avoided in the preparation of aluminacarriers of this invention.

In the overall transition between the alumina trihydrates and alphaalumina, several different transitional aluminas are prepared, eithersimultaneously or concurrently. Some of these transitional phases areconvertible to others upon proper heating or cooling. It is immaterialin the practice of my invention which particular transi tional aluminais used so long as the carrier predominantly consists of at least onetransitional form and so long as the content of alpha alumina in thecatalyst is kept at a minimum.

According to the nomenclature used in the pamphlet, Alumina Properties,"Russell et al., published by the Aluminum Company of America,Pittsburgh, Pa., 1956, the names assigned to the various transitionalaluminas are gamma, delta, eta, theta, kappa, chi and rho. All these areuseful as carriers in my invention. In addition, the alpha monohydrateitself is in a sense a transitional alumina, since it is a productreversibly obtained on heating of either alpha or beta aluminatrihydrate under suitable conditions of temperature and time. The alphamonohydrate is also useful as an alumina carrier of this invention. Inaddition to the transitional forms described above, there is anamorphous alumina which is characterized by having no definitive X-raydiffraction pattern. This amorphous material is usually present alongwith the transitional aluminas of this invention and for purposes ofthis invention is included among them.

Any of the transitional aluminas mentioned above can be used singly as acarrier of this invention. I ordinarily prefer, however, to use mixturesof two or more of the transitional aluminas including mixtures of asmany as nine. Indeed, in any practicable method of preparation, amixture of at least two, and usually more than two, is perforce formed.

It appears not possible to describe each transitional alumina in termsof its specific physical properties, other than those mentioned above.Many can be characterized by their X-ray diffraction pattern. Several ofthese are reproduced on page 28 of the pamphlet referred to above.

It is likewise not possible to ascribe definite preparative proceduresto preparation of the transitional aluminas of this invention.Conversion of the starting materialsalpha and beta alumina trihydratesand alpha alumina monohydrate-to one or more of the transitionalaluminas of this invention, as well as conversion of one transitionalalumina to another is a function of both time and temperature. Heatingto a high temperature for a short time could result in a mixture oftransitional aluminas having the same composition as is produced byheating the same starting mixture or ingredient to a given lessertemperature for a longer time. Generally speaking, alpha aluminatrihydrate is converted to the alpha monohydrate at about 140 C. in airor superheated steam and at about 100 C. in vacuum. Beta aluminatrihydrate appears to [be readily converted to the alpha monohydrate atabout l20160 C. Heating of the alpha trihydrate to about 140 C. for onehour results in some conversion to the chi transitional form. The chiform in turn, goes over to some extent to the kappa transitional aluminawhen heated to 500 C. for one hour. Heating of the alpha monohydrate forone hour at 250 C. gives some gamma, which on heating at 850 C. for thesame length of time produces some theta transitional alumina, withpossible intermediate conversion to delta. Heating of the betatrihydrate to 140 C.,

,in addition to producing some alpha monohydrate, also produces some ofthe eta activated form. This in turn goes over to theta on heating at450 C.

The kappa and theta forms are converted to the alpha alumina, not usefulin this invention, on heating to 1150 C. for one hour.

In general then, the transitional aluminas used in this invention areprepared by heating a starting alumina se lected from the classconsisting of alpha alumina trihydrate, beta alumina trihydrate andalpha alumina monohydrate to a temperature of at least -150 C. for aperiod of time sufficient to permit substantial conversion to atransitional alumina but insufiicient to convert a substantial fractionof the transitional aluminas irreversibly to the active alpha alumina.In general, prolonged heating above about 1000 C. should be avoided. Mycarriers in some cases may contain small amounts of either the startin gmaterial or alpha aluminas, or both.

In addition to the inherent transitional nature of the alumina itself,certain other properties. are essential for use as carriers of thisinvention. The most important of these appears to be the surfacearea/mass ratio and the content of silica, SiO The transitional aluminaswhich we use are those whose surface area/mass ratio is at least 75 m g.and those having a silica content of from 0.01 to about 5 percent. Inorder to function efficiently according to my invention, thetransitional alumina must meet both these criteria. If the surface isgreater than the above minimum but the silica content greater than theabove maximum, the alumina does not function well. By the same token, ifthe silica content is 5 percent or below but the surface area is below75 m. /g., the alumina does not function as a carrier of this invention.Nor does it so function if neither the silica content nor the surfacearea is within the above specifications.

In illustration of the importance of the above properties, I have testedaluminas with surface areas as high as 350 m. g. but with silica contentgreater than 5 percent. These have resulted in catalysts with inferiorproperties with respect to exhaust gas conversion. Also, an alumina witha silica content less than 5 percent but with a surface area of only .5m. g. was ineffective as a support for copper oxide.

Certain aluminas meeting the requisites of this invention arecommercially available. Included in these are those sold by AluminumCompany of America as Desiccant Grade Active Aluminas; Grade Fl, F-3,and F-10, and by the Kaiser Aluminum Company as KA-101. The above Faluminas are made by the controlled calcination of a rocklike form ofalpha alumina trihydrate. See the Russell et al publication referred toabove. Analyses and physical properties of typical aluminas of thisinvention are:

CHEMICAL ANALYSIS Percent A1 0 85.0-95.4 Na O 0.4-2.0 F6203 SiO 0.02-5Loss on ignition, 1100 C 4.2-8.5

PHYSICAL PROPERTIES Surface area, m. g. 75-360 Form Granular or ballsBulk density, lb./ft. 43-57 Specific gravity 3.13.3

Pore volume, ml./g. 1 025-03 Dynamic sorption, percent 11-23 Porediameter, A 40-50 Crushing strength, percent 5566 One method oflarge-scale preparation of the alumina carriers of this invention is asa by-product of the Fickes- Sherwin modification of the Bayer process inthe manufacture of metallic aluminum. During the process, the aluminumtrihydrate is precipitated from alkali aluminate solutions. Thismaterial, a scale-like deposit, is then crushed or ground, and calcinedat a temperature between 300 and 800 C. The finished material is usedprimarily as a commercial adsonbent. It does not readily pack, can beused in high pressure applications, and after use, can be readilyregenerated.

The granular transitional aluminas I use as the carrier material for mycatalysts may be from about 2.5 to 8 mesh. (Tyler Standard Screen ScaleSieves). However, I have found materials of from 4 to 6 mesh to beoptimum for this exhaust gas application.

An important property of any catalyst is its resistance to attrition andabrasion. This is particularly true with an automobile exhaustapplication because of the continual agitation and physical shocks towhich the catalyst bed is subjected. While the granular form oftransitional alumina is an excellent material for this application, wehave found that the ball form is particularly resistant to attrition andabrasion. An example of the ball form of transitional alumina is thatsold by the Kaiser Aluminum Company as Activated Alumina KA-lOl. Thismaterial is prepared by the controlled calcination of beta trihydrate,and its finished form is composed mainly of eta alumina and alphamonohydrate. The final product has low silica and titanium dioxidecontent, 0.02 and 0.002 percent, respectively. Its high surface area andextreme resistance to abrasion make it admirably suited for an exhaustgas application. The material has a hard uniform surface, crushingstrength of 66 percent, and excellent thermal stability properties. Thesphericity of the active alumina balls eliminates, or reduces to aminimum, the chipping which is evident when using a bed consisting of agranular material. However, the uniform sphericity reduces packing andchanneling, resulting in lower pressure drop as compared to a granularcatalyst bed. Active aluminas of from about to inch in diameter ormixtures of alumina balls in this range are suitable for thisapplication. However, I prefer to use those ranging in size from /8 to Ainch. Thus, a preferred embodiment of this invention is a catalystespecially suited for exhaust gas conver sion, said catalyst consistingof ball form transitional alumina of from to inch, preferably from toinch, in diameter, said alumina having a surface area of at least 75 m.g. and containing from. 0.01 to about percent silica, and being mixed orimpregnated with from 0.5 to 25 percent copper in an oxide form.

I further prefer, under certain conditions of operation, to use in thesame catalyst bed copper oxide impregnated on two or more forms oftransitional alumina. Some ball forms of alumina may have superiorproperties with respect to attrition whereas some granular forms may besuperior with respect to oxidation efiiciency. By using both forms ofalumina the advantages of resistance to attrition and abrasion of theball form and the superior oxidation efiiciency of the granular form arecombined. The different forms of aluminas may be mixed prior to catalystpreparation or jointly impregnated and decomposed to form the finishedcatalyst. Also, the two catalysts may be prepard independently and mixedafter final preparation. The two forms of catalysts may be mixedrandomly to form the bed or they may be Stratified, horizontally orvertically. The front portion of the bed may be composed of one form andthe rear portion of the other form and vice versa. I prefer to have thefront portion of the bed composed of a catalyst prepared by using a ballform of alumina and the rear part of the catalyst using the granularform of the alumina as the carrier. By this technique the pulsating andabrasive effect of the entering gas stream is eliminated or reduced to aminimum, being absorbed by the more resistant ball form and the overallefficiency of the bed is maintained at a high level by the moreefiicient granular form which composes the rear part of the bed. Thus,another preferred embodiment of this invention is a catalyst especiallysuited for exhaust gas conversion wherein the front 2 to 40 percentportion of the catalyst bed consists of a catalyst using as a carriermaterial, the

ball form of transitional alumina of from to preferably from A; to 4inch in diameter and the rear 60 to 98 percent portion of said catalystbed consists of a catalyst prepared by using a granular transitionalalumina of from 2.5 to 8, preferably from 4 to 6 mesh, both said ballform and granular form of transitional alumina having a surface area ofat least m. /g. and containing from 0.01 to about 5 percent silica, bothsaid transitional aluminas being impregnated with from 0.5 to 25 percentcopper in an oxide form.

I have also found that, under certain conditions, the inclusion of asmall amount of another metal or metals may further enhance theproperties of my catalysts. The additional metal or metals act as apromoter; that is, though in themselves they may have little activity,they impart better characteristics to the finished catalyst. Generally,promoters serve to improve the activity, stability or selectivity forthe reaction in question and oftentimes it is difficult to make adistinction as to their specific function. I have found that theinclusion of up to 10 percent, based on the total weight of thecatalyst-carrier system, of a promoter metal or metals may to a degreeimprove efiiciency and life of the catalysts of this invention. Thepromoter in the finished catalyst is usually in an oxide form but insome cases, e.g., silver, it may exist as the free metal. Metals thatmay be used as promoters include sodium, lead, potassium, magnesium,calcium, strontium, barium, platinum, titanium, chromium, zirconium,iron, cobalt, nickel, manganse, zinc, cadmium, germanium, tin, silver,cesium, gallium, vanadium, scandium and the Lanthanide Series ofElements, including yttrium, lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holrnium, erbium, thulium, ytterbium, and lutetium (see pages 891-893 ofInorganic Chemistry by Theraild Moeller, John Wiley & Sons, Inc., NewYork, NY. (1952), and the like including metals from Groups I, II, III,IV, V, VI, VII and VIII of the Periodic Table of the Elements. Thesemetals may be introduced before or during preparation of the catalystsas salts such as the nitrate, acetate, carbonate, and the like, or inthe form of oxides or hydroxides, or even in some cases as the finelydivided metal itself. The salt of the second metal must be judiciouslyselected so as to avoid the formation of a precipitate.

The following examples illustrate methods of preparing the catalysts ofthis invention.

Example I F-l grade alumina is used as the carrier of this example. Thistransitional alumina has about 92 percent A1 0 about 0.8 percent Na O,about 0.12 percent Fe O and about 0.09 percent SiO On ignition, it losesabout 6.0 percent of its weight. It is a granular material having asurface/mass ratio of about 210 m. /g. Its bulk density (packed) isabout 55 lb./ft. and its specific gravity is about 3.3. It is preparedby calcination of alpha alumina trihydrate and contains a mixture of thetransitional aluminas described earlier in this specification. Asolution comprising 5 parts of ammonium carbonate and 18 parts ofaqueous ammonium hydroxide (28 percent NHg) is prepared. Eleven parts ofmalachite [CuCO Cu(OH) is dissolved in the solution. At this point adeeply violet-colored solution is formed. The copper is in solution asthe complex tetrammines copper (II) carbonate of about percent copper inan oxide form impregnated on transitional alumina.

Example 11 The procedure of Example I is followed but amounts of basiccopper carbonate, ammonium hydroxide and ammonium carbonate are usedsuch that the finished catalyst is composed of 25 percent copper in anoxide form.

Example 111 The procedure of Example I is followed but amounts of basiccopper carbonate, ammonium hydroxide and ammonium carbonate are usedsuch that the finished catalyst is composed of 0.5 percent copper in anoxide form.

Example IV A transitional alumina composed of alpha alumina monohydrate,amorphous alumina and small quantities of gamma and theta transitionalalumina is mixed with a solution of the azurite form of basic coppercarbonate [2CuCO -Cu(OH)2], ammonium hydroxide and am moniurn carbonate.The procedure of Example I followed. The finished catalyst istransitional alumina impregnated with oxides of copper, comprising byweight 10 percent copper in an oxide form.

Example V Cuprous oxide, Cu O, is dissolved in a solution of ammoniumcarbonate and ammonium hydroxide. The highly soluble diammine cuprouscarbonate, [Cu(NH CO is formed. The procedure of Example I is thenfollowed. The finished catalyst is transitional alumina impregnated with12 percent copper in an oxide form. The transitional alumina is derivedfrom the calcination of beta alumina trihydrate and containspredominantly the eta and theta transitional aluminas along with somealpha alumina monohydrate.

' Example VI F3 alumina is mixed with a solution prepared from cupricoxide, ammonium hydroxide, and ammonium carbonate and the procedure ofExample I is followed. This particular granular transitional alumina hasessentially the same elemental analysis as the alumina of Example I.

surface area, is about 200 m. g. It is made by controlled calcination ofalpha alumina trihydrate and contains a mixture of transitionalaluminas. The finished catalyst is F3 alumina impregnated with oxides ofcopper comprising by Weight 7 percent copper in an oxide form.

Example VII silica.

Example VIII A solution of malachite [CuCO Cu(OI-I) in aqueous ammoniumhydroxide and ammonium carbonate. is prepared. Chromic nitrate is addedto this solution. Transitional alumina is introduced into .the resultingmixture, and the procedure of Example I is followed. The finishedcatalyst is transitional alumina impregnated with oxides of copper andchromium, comprising by weight percent copper and 10 percent chromium.The transitional alumina base, KA-lOl, is made by controlled phase con-.version of beta alumina trihydrate, and its primary transi- 'Its losson ignition is about 7.2 percent by weight, and its 1o tionalsubstituents are the eta form and alpha alumina monohydrate.

Example IX A mixture of malachite [CuCO Cu(OlH) and azurite [2CuCO-Cu(OH) is dissolved in a solution of ammonium hydroxide and ammoniumcarbonate. Silver acetate is added to this solution. Transitionalalumina is then introduced and the procedure of Example I followed. Thistransitional alumina is made by conversion of a mixture of alpha andbeta alumina trihydrate and contains substantially all the transitionalaluminas, including amorphous alumina and alpha alumina monohydrate. Thefinished catalyst is transitional alumina impregnated with oxides ofcopper and silver, comprising by Weight 8 percent copper and 1 percentsilver.

Example X Copper acetate is dissolved in ammonium hydroxide to form thedeeply violet-colored, highly soluble diammine copper (II) acetate[Cu(NH (C H O The procedure of Example I is followed. The finishedcatalyst of this example is F-l transitional alumina impregnated with 12percent by weight copper in an oxide form.

Example XI KA-lOl alumina is used as the carrier in this example. Thistransitional alumina has about 95.4- percent A1 0 about 0.02 percent SiOabout 0.02 percent F 0 about 0.002 percent TiO and 0.40 percent Na O. Onignition it loses about 4.2 percent of its weight. It is a ball form oftransitional alumina having a surface area of about 360 m. g. Its bulkdensity is about 43 lb./ft. and has a dynamic sorption of about 19.7percent. Its crushing strength is 66 percent. It is prepared by thecarefully controlled calcination of beta trihydrate and its principleconstituents are eta alumina and alpha monohydrate. One-sixteenth inchdiameter balls are immersed in a solution of malachite, ammoniumcarbonate and ammonium hydroxide and the procedure of Example I isfollowed. In this example the finished catalyst is inch diameter ballform of transitional alumina impregnated with 6 percent copper in anoxide form.

Example XII The procedure of Example XI is followed but the carriermaterial for this catalyst is KA101 ball form of transitional aluminahaving a diameter of approximately inch. The amounts of startingmaterials used in this present example are such that the finishedcatalyst contained 12 percent by weight of copper in an oxide form.

Example XIII Example XIV The procedure of Example XIII is followed butthe starting materials are such that the finished catalyst contains 7percent copper and 6 percent cobalt in oxide forms.

Example XV A solution of basic copper carbonate, amomnium carbonate,ammonia, and cobalt carbonate is formed. To this is added a solution ofammonium metavanadate and oxalic acid. KA-l01 alumina is immersed in thesolution and allowed to stand so as to be thoroughly impregnated. The

1 1 excess liquid is drained away and the remaining mixture is heated upto about 600 C. to effectuate decomposition. The finished catalyst iscomposed of 8 percent copper, 3.8 percent cobalt, and 0.5 percentvanadium, all in oxide forms.

Example X V1 The procedure of Example XV is followed but the quantitiesof starting materials are used such that the finished catalyst contains12 percent copper, 6 percent cobalt, and 3 percent vanadium, all inoxide forms.

The catalysts of this invention are eminently suited to catalyze theoxidation of hydrocarbons and carbon monoxide found in the exhaust gasstream of internal combustion engines. Carbon monoxide is poisonous andis particularly dangerous to human health because it is ditiicult todetect, being colorless and essentially odorless. Hydrocarbons, thoughin themselves somewhat less toxic and harmful, can be asphyxiants, ifconsumed in large volumes. More important is their tendency, by reactingwith other atmospheric constituents, to substantially contribute to airpollution. Among the more important detrimental effects attributed toair pollution are damage to property through corrosion, toxicity towardcrops and plant life in general, soiling of surfaces, restrictedvisibility, etc. Even more serious are the effects on human physiology.In a milder state, air pollutants, besides having noxious odors, areirritants to the eyes, ears, nose and throat. In more extreme cases,damage to health has been directly attributed to air pollution. One formof air pollution, a hazelike formation, has been evidenced in certainlarge cities and is referred to as photochemical smog.

The quality and quantity of unburned and partially oxidized hydrocarbonsand carbon monoxide varies widely dependent upon vehicle operatingconditions and the conditions of maintenance of the engine. For example,under idle conditions the concentration of unburned hydrocarbons in theexhaust gas may be as low as 300 parts per million; whereas, underdecelerating conditions the concentration may be over 5,000 parts permillion. Moreover, depending on operating conditions, a variety ofpartial oxidation products are present in the exhaust gas stream. Thefailure of just one sparke plug to fire will greatly increase theemission of these noxious products.

Among the major requisites for a system employing a catalyst to oxidizethe deleterious materials found in exhaust gas streams of automobilesare the following:

( 1) Oxidation of substantial amounts of hydrocarbons and carbonmonoxide.

(2) The oxidation should be complete, as intermediate products undergofurther reactions with other atmospheric constituents and therebysubstantially contribute to smog formation.

(3) The discharged exhaust gas should be free of noxious odors.

(4) The catalyst should be active at relatively low temperatures andthermally stable at relatively high temperatures.

(5) It must operate effectively under a wide variety of conditions ashydrocarbon and carbon monoxide content of exhaust gas variestremendously, depending on whether the car is idling, accelerating,cruising, or decelerating.

(6) The catalyst must be highly resistant to poisonous effects of theoxidation products of the many constituents found in gasoline.

(7) The catalyst must be particularly resistant to lead salts, both aspoisons and as coating materials.

(8) It should preferably not oxidize nitrogen.

(9) The catalyst material should be highly resistant to attrition due otphysical shock.

The high degree of efficiency of my catalysts for an exhaust gasapplication is shown by the following test: The exhaust gas of a CFR-Lhead, 7:1 compression ratio single cylinder engine was passed over acatalyst bed consisting of 42 cubic inches of the catalyst material. Asecondary air supply to provide oxygen for the oxidation was introducedinto the exhaust gas stream just prior to the catalyst bed. This airsupply was constant throughout the testing period. During the test theengine was continually cycled, 50 seconds under idling conditions, and150 seconds at wide-open throttle. The operating conditions for the testis as follows:

TABLE I.ENGINE OPERATING CONDITIONS 42 cu. in. catalyst bed test IdleWide open throttle My experience has shown that many catalysts areeffective for the oxidation of deleterious exhaust gas constituents whenthe engine is operated on a fuel free from, or relatively low, in sulfurand organolead antiknock compounds. However, the oxidation products ofthe organolead compounds and sulfur commonly found in gasolines arepoisonous to most catalysts. In an accelerated test to determine theresistance of the catalysts under investigation to lead and sulfurcompounds, the engine was operated on a fuel containing the relativelyhigh amounts of 12 grams of lead per gallon as tetraethyllead and 0.12percent by weight sulfur. With respect to the concentrations of sulfurand lead compounds, the conditions of this test are much more severethan would be encountered in a commercial application wherein fuelscontain from about 2 to 4 grams of lead per gallon and from about 0.03to 0.07 percent -by weight sulfur.

The composition of the fuel on which the engine was operated during thistest is as follows.

FUEL COMPOSITION ASTM distillation: F.

During the entire test,.the engine was operated under the conditionsshown in Table I. The hydrocarbon and carbon monoxide concentrations ofthe exhaust gas stream were measured before and after passage throughthe catalyst bed. The measurements were obtained under equilibriumconditions at wide-open throttle. The high oxidation efiiciencies of thecatalysts of this invention are illustrated by the data summarizedbelow.

TABLE II.OXIDA'IION EFFICIENCIES OF COPPER OXIDE ON TRANSITIONAL ALUMINACATALYST Time, hours Percent reduction of hydrocarbons Percent reductionof varbon monoxide The results of this test serve to illustrate the highdegree of efficiency of the catalysts of this invention. Even tent, say3 grams per gallon and 0.05 weight percent sulfur, oxidationefliciencies are even higher. The same is of course true of lead-freeand sulfur-free fuels.

An important feature of the catalysts of this invention is theirexcellent thermal stabilities. The catalysts bed temperature undernormal engine operation may vary from 400 to 1700 F. Under extremeconditions of severe acceleration and deceleration, bed temperatures ashigh as 1750 F. have been observed. Using catalysts ofthis invention,catalyst beds have been operated at temperatures at least this high withno apparent damage to the activity of the catalyst. Heat stability isvery important because it obviates the necessity of installing amechanical system to have the exhaust gas by-pass the catalyst bed incase of extremely high temperatures. Such a by-pass system would berequired if the catalyst were susceptible to damageat high temperatures.Good thermal stability is also desirable in that it allows the reactionto be carried out at higher temperatures wherein higher efficiencies maybe attained. Furthermore, this property becomes important whenconsidering the design of a commercial 've hicle exhaust systemincorporating an oxidation catalyst. The additional heat from theoxidation process would naturally tend to overheat the passengercompartment. This problem could be solved by insulating the catalyst bedand exhaust system. Of course this would be possible only if thecatalyst could tolerate the higher temperatures due to the insulation.

Still another important feature of the catalysts of this invention istheir ability to catalyze reactions at extremely low temperatures. Sincecatalyst activity generally increases with temperature, in manyapplications it can be optimized by the simple expediency of increasingreaction temperatures. However, in exhaust gas conversion, temperaturescannot readily be controlled and a rather anomalous requisite of highactivity at both low and high temperatures is imposed. The catalysts ofthis invention are active at a temperature as low as 350 F. i.e.,temperatures below that of the exhaust gas stream. At temperatures of450 F. and above, catalyst efliciency markedly improves. Of course, asthe oxidation starts, the heat of reaction serves to raise bedtemperatures to a much higher level.

Another feature of the catalysts of this invention is their ability tocatalyze the oxidation of nitrogen. This is an important consideration.Oxides of nitrogen, and their subsequent reaction products readilycontribute to the formation of photochemical smog and are eye andrespiratory irritants.

Catalysts of this invention have been tested under actual operatingconditions in modern automobiles with excellent results; namely,substantial and essentially complete oxidation of hydrocarbons andcarbon monoxide, a discharge exhaust gas substantially free of noxiousodors, activity at both high and low temperatures and under a widevariety of operating conditions and resistance to poisons in the exhauststream, particularly lead salts and sulfur compounds. The resistance toattrition of the catalysts of this invention is such that specialmechanical contrivances are not required to safeguard the catalystmaterial. The catalyst is simply put into a suitable container withopenings to receive and discharge the exhaust gases. To firmly retainthe catalyst material, the receiving and discharge openings are coveredwith wire screening. The container may have internal bafiling to allowgreatest contact between catalyst and exhaust gas, and/ or to use thehot reaction gases to heat the incoming exhaust gases. The container mayactually replace the vehicle mufiler, or it may be incorporated into theconventional exhaust system of current vehicles. The catalyst bed mayalso be located in the exhaust manifold or in the tailpipe of theexhaust system.

To aid the oxidation, secondary air is usually introduced into thesystem to obtain maximum efficiency. This is accomplished by the use ofa variable speed blower, so that the amount of secondary air varies withoperating conditions. The secondary air supply may also be introduced asa natural flow through the use of an appropriate air scoop or the like.

My catalysts can be used to convert the exhaust gas of any gasolines.The gasolines can be of the aliphatic, aromatic and olefinic typeincluding both straight run and catalytically produced gasolines and anyand all mixtures thereof. The gasolines can contain the usual additivesincluding organolead and other antiknock agents such as tetraethyllead,tetraphenyllead, tetramethyllead, mixtures of alkylleads, such astetraethyllead-tetramethyllead mixtures, ferrocene, cyclopentadienylmanganese tricarboyl, cyclopentadienyl nickel nitrosyl, scavengers,antioxidants, dyes, deposit modifiers, including trimethylphosphate,dimethylphenylphosphate and the like.

In addition to use in spark ignition internal combustion engines, thepresent catalyst may also be used to reduce or eliminate unburnedhydrocarbons and carbon monoxide from the exhaust products of combustionprocesses in general. This includes the compression ignition engine, oiland coal furnaces, residual fuel burners, etc.

I claim:

1. A method for producing a catalyst, which comprises comminglingaqueous ammonia and a carbonate of copper, impregnating an alumina basewith the resultant mixture, drying the impregnated base to compositewith the base a compound of copper and then calcining the dried base toform a composite of alumina and an oxide of copper.

2. A method for producing a catalyst, which comprises comminglingaqueous ammonia and copper carbonate, impregnating an alumina base withthe resultant mixture in an amount to form a final catalyst containingabout 0.5 to 25 percent copper in an oxide form, drying the impregnatedalumina, and then calcining the dried impregnated alumina to form acomposite of alumina and an oxide of copper.

3. In the manufacture of a catalyst consisting essentially of transitionalumina impregnated with copper oxide, the process which consistsessentially of forming a deeply violet-colored solution by reacting, inthe presence of water, an essentially insoluble copper compound selectedfrom the class consisting of copper oxides, copper hydroxide and coppercarbonates with an ammoniacal reagent selected from the class consistingof ammonia, ammonium hydroxide and ammonium carbonate, said solutionbeing characterized in that substantially the only anions present areselected from the class consisting of carbonate anions and hydroxideanions, impregnating said transition alumina with said solution,removing supernatant solution from said alumina, and then heating theresidual product whereby copper oxide is formed therein, said transitionalumina being of the activated type and having a surface area of atleast 75 square meters per gram and a silica content of 0.01 to about 5percent.

4. The process of claim 3 wherein said reactant copper compound is abasic copper carbonate, and said ammoniacal reagent consists of asolution of ammonium carbonate and ammonium hydroxide.

5. The process of claim 4 wherein said reactant copper compound is themalachite form of basic copper carbonate.

6. The process of claim 4 wherein said reactant copper compound is theazurite form of basic copper carbonate.

7. The process of claim 4 wherein said reactant is a mixture of themalachite and azurite forms of basic copper carbonate.

8. The process of claim 3 wherein said reactant cop- 15 per compound iscuprous oxide, GU 0, and said ammoniacal reagent consists of a solutionof ammonium carbonate and ammonium hydroxide.

9. The process of claim 3 wherein said reactant copper compound iscopper oxide, CuO, and said ammoniacal reagent consists of a solution ofammonium carbonate and ammonium hydroxide.

10. A catalyst composition especially adapted to catalyze the oxidationof exhaust gases, said composition consisting essentially of transitionalumina impregnated with 0.5 to 25 percent by weight of copper in anoxide form, said copper oxide being characterized by having been formedby heating a residual product formed in turn by impregnating atransition alumina of the activated type and having a surface area of atleast 75 square meters per gram and a silica content of 0.01 to about 5percent with a deeply violet-colored solution formed by reacting, in thepresence of water, an essentially insoluble copper compound selectedfrom the class consisting of copper oxides, copper hydroxide and coppercarbonates with an ammoniacal reagent selected from the class consistingof ammonia, ammonium hydroxide and ammonium carbonate, said solutionbeing characterized in that substantially the only anions present areselected from the class consisting of carbonate anions and hydroxideanions.

11. The composition of claim wherein said insoluble copper compound is abasic copper carbonate and said ammoniacal reagent is a mixture ofammonium carbonate and ammonium hydroxide.

12. The composition of claim 10 wherein said insoluble copper compoundis selected from the class consisting of malachite, azurite, and amixture of the two and said ammoniacal reagent is a mixture of ammoniumcarbonate and ammonium hydroxide.

13. The composition of claim 10 wherein said insoluble copper compoundis cuprou's oxide, Cu O, and'said ammoniacal reagent is a mixture ofammonium carbonate and ammonium hydroxide.

14. The composition of claim 10 wherein said insoluble copper compoundis copper oxide, CuO, and said ammoniacal reagent is a mixture ofammonium carbonate and ammonium hydroxide.

15. The composition of claim 10 wherein said insoluble copper compoundis selected from the, class consisting of malachite, azurite, and amixture of the two, said ammoniacal reagent is a mixture of ammoniumcarbonate and ammonium hydroxide, and said transition alumina consistsessentially of sperical particles of from to /3 inch in diameter.

References Cited UNITED STATES PATENTS 1,589,644 6/1926 Hcdenburg 23611,937,728 12/1933 Storch 252-476 2,034,077 3/1936 Arnold et a1 252-4762,696,475 12/1954 Farrow 252-463 2,730,429 1/1956 Abraham 2361 2,800,5187/1957 Pitzer 252463 2,847,475 8/1958 Voge et a1. 252-463 3,133,0295/1964 Hoekstra 252-466 EDWARD J. MEROS, Primary Examiner.

OSCAR R. VERTIZ, MAURICE A. BRINDISI,

JULIUS GREENWALD, Examiners.

G. T. OZAKI, R. D. LOVERING, Assistant Examiners.

1. A METHOD FOR PRODUCING A CATALYST, WHICH COMPRISES COMMINGLINGAQUEOUS AMMONIA AND A CARBONATE OF COPPER, IMPREGATING AN ALUMINA BASEWITH THE RESULTANT MIXTURE, DRYING THE IMPREGNATED BASE TO COMPOSITEWITH THE BASE A COMPOUND OF COPPER AND THEN CALCINING THE DRIED BASE TOFORM A COMPOSITE OF ALUMINA AND AN OXIDE OF COPPER.
 10. A CATALYSTCOMPOSITION ESPECIALLY ADAPTED TO CATALYZE THE OXIDATION OF EXHAUSTGASES, SAID COMPOSITION CONSISTING ESSENTIALLY OF TRANSITION ALUMINAIMPREGNATED WITH 0.5 TO 25 PERCENT BY WEIGHT OF COPPER IN OXIDE FORM,SAID COPPER OXIDE BEING CHARACTERIZED BY HAVING BEEN FORMED BY HEATING ARESIDUAL PRODUCT FORMED IN TURN BY IMPREGNATING A TRANSITION ALUMINA OFTHE ACTIVATED TYPE AND HAVING A SURFACE AREA OF AT LEAST 75 SQUAREMETERS PER GRAM AND A SILICA CONTENT OF 0.01 TO ABOUT 5 PERCENT WITH ADEEPLY VIOLET-COLORED SOLUTION FORMED BY REACTING, IN THE PRESENCE OFWATER, AN ESSENTIALLY INSOLUBLE COPPER COMPOUND SELECTED FROM THE GLASSCONSISTING OF COPPER OXIDES, HYDROXIDE AND COPPER CARBONATES WITH ANAMMONIACAL REAGENT SELECTED FROM THE CLASS CONSISTING OF AMMONIA,AMMONIUM HYDROXIDE AND AMMONIUM CARBONATE, SAID SOLUTION BEINGCHARACTERIZED IN THAT SUBSTANTIALLY THE ONLY ANIONS PRESENT ARE SELECTEDFROM THE CLASS CONSISTING OF CARBONATE ANIONS AND HYDROXIDE ANIONS.